1. Field of the Invention
This invention relates, in general, to color printers and plotters and, more specifically, to apparatus and methods for creating a specific pixel pattern on a hard copy output medium.
2. Description of the Prior Art
Color printers, plotters, duplicators, electronic copiers, and like devices usually are limited in the sharpness they can produce on the hard copy output medium because of the resolution of the image-producing device, or printhead. Many of the printheads associated with such color machines can also print pure or true black in addition to color component or process black. However, even when using true black in a color machine, the resolution of the pixels is not usually better than that achieved when the printhead is operating in the full color mode. Thus, the overall sharpness of the produced image is largely governed by the basic resolution of the printhead.
Because true and process black pixels produce substantially the same stimuli in the observer, either system can be used to produce black in the printed image. Because of registration considerations, and for other reasons, machines capable of producing both types of black usually use true black to represent blacks in the image when possible. This produces a black which is free from colored borders caused by misregistration, but the resolution and resulting sharpness is not significantly better than that achievable with process color printing.
In order to improve the sharpness of the printed image, it is desirable, and it is an object of this invention, to provide a printhead assembly which can use both the true and process black capabilities of the printhead to effectively double the resolution of the printhead without adding to the complexity of the printhead or increasing the overall number of pixel-producing elements in the printhead.